On Monday, March 20th, American pharmaceutical companies Sanofi-Aventis US, a subsidiary of France-based Sanofi S.A. (NYSE:SNY), and Regeneron (NASDAQ:REGN) were listed as plaintiffs in a suit filed to seek declaratory judgment of non-infringement of a patent held by American biopharma firm Amgen (NASDAQ:AMGN). Sanofi-Aventis and Regeneron are hoping to protect their market interest in a treatment developed to help patients suffering from atopic dermatitis; a skin condition which the suit calls “a debilitating, disfiguring disease,” in the face of what they believe is a likely patent challenge from Amgen. The case has been filed in the U.S. District Court for the District of Massachusetts (D. Mass.).

A Complaint filed

The complaint filed by Sanofi-Aventis and Regeneron seeks a declaration of non-infringement of Amgen’s U.S. Patent No. 8679487, titled Anti-Interleukin-4 Receptor Antibodies. Issued in March 2014, it discloses an isolated human antibody with a reference antibody for binding to human interleukin-4 (IL-4) receptor, the reference body having a heavy chain and a light chain composed of specific amino acid sequences. The antibody is a useful treatment for a variety of disorders to which IL-4 activity contributes, including atopic dermatitis.

Sanofi-Aventis and Regeneron have been developing Dupixent, a monoclonal antibody which received a breakthrough therapy designation by the U.S. Food and Drug Administration (FDA) in November 2014 for the treatment of atopic dermatitis. Phase 3 clinical trials of Dupixent lasting 16 weeks resulted in nearly 40 percent of atopic dermatitis patients seeing complete or near complete removal of skin lesions caused by the form of eczema. In early March, the two pharmaceutical firms announced successful results of a year-long trial of Dupixent in atopic dermatitis patients.

Major cause behind the suit

The major impetus behind this suit was Sanofi-Aventis and Regeneron’s discovery that Amgen hired litigation counsel to assert the ‘487 patent and is also working on retaining experts. The plaintiffs believe that the only likely target for any potential Amgen infringement suit asserting the ‘487 patent would target Dupixent, “the only IL-4 inhibitor expected to come to market in the near future.”

In arguing that Dupixent falls outside of the claims of the ‘487 patent, the plaintiffs suggest that the proper construction of the claims would only cover the specific antibody structures mentioned in the specification of the ‘487 patent. Despite the fact that all 17 claims of the ‘487 patent are directed at an IL-4 inhibiting antibody, the claims only recite the antibody in terms of its functional activities and the markedly different structure of Dupixent is cause for a finding of non-infringement.